Machine Type Communication (MTC) is a work item being studied in 3GPP (3rd Generation Partnership Project), targeting cellular based Machine to Machine communication (M2M). The machine devices may be located in the basement with higher penetration loss than the current cell edge UEs. To support these devices, coverage enhancement techniques are needed.
One of the techniques to enhance the coverage is repetition. At the receiver side, the repetitive control information packets are combined and decoded for better performance. It is spectrally efficient to have various levels of repetition for UE located under various radio conditions.
Random access procedure includes four types of message exchange: preamble transmission in uplink, random access response (RAR) transmission in downlink, message 3 (e.g. RRC connection request) in uplink, and contention resolution message in downlink. Each of these messages may require numerous repetitions.
In current communication systems, eNB defines a RAR time window during which UE performs blind decoding in order to obtain the RAR message. Also, in current communication systems, physical downlink control channel (PDCCH) and RAR messages for the same UE are transmitted in the same sub-frames.